Studies of innercity Black Americans proposed here: (1) address the epidemiology of HIV infection and its related transmission practices; (2) monitor 2-year change in these; (3) specifically compare the risk behaviors of untreated and treated drug users; (4) investigate interrelationships cross-sectionally and longitudinally between AIDS-specific motivational factors, communication networks, and related sociodemographic attributes - - for the objective of contributing to strategies to prevent the spread of HIV infection. Specific studies include: epidemiologic analysis of rates and distribution of HIV seropositivity, a relative risk analysis of infection-related transmission behaviors, and causal analysis of the role of cognitive and affective influences (formulated in a Health Beliefs Model) and their social contextual antecedents (e.g., social networks and social roles). Studies will be performed at two points in time, to provide both baseline and change estimates, using data collected through interviews and blood serum assays with a community representative sample of approximately 400 innercity nonHispanic Black Americans. This is a longitudinal cohort with detailed health, drug use and life histories developed over 15 years and three study waves prior to this proposal. Findings from the longitudinal cohort will be supplemented with a case-control study at a single time point (N=300) of racially and age similar patients drawn from the local municipal hospital.